USPS has been giving free supplies for years. However they do not give out tape anymore. They stopped that a few years back.
But if you get to know your postal employees and they see you ship a lot like me then you can ask for free priority tape at the counter and more than likely they'll give you a roll or two.

They don't really work like that. To do so would require that you break one of the corners, and you would lose structural strength and stability, even after attempting to tape it back together. It would most likely be more trouble than its worth anyway, but for priority mail they are nice.